make vertices have the same number of weights
Bones deform vertices that belong to a vertex group of the same name as the bone. You can manually assign and adjust the weight a vertex has for each group.

While in edit mode the vertex groups panel looks like this -



The assign button will assign the selected vertices to the selected group with the current weight setting. The remove button will remove the selected vertices from the selected group.

In the properties sidebar there is a Vertex Weights panel that can help, it can be elusive as it only shows if a single selected vertex is assigned to one or more vertex groups or multiple selected vertices that belong to the same group (only the one common group will show).



There is also the show vertex groups weight addon which you can download from here.